WASHINGTON — Early in the 2008 campaign, when high hopes hadn't given way to harsh realities, presidential candidate Joe Biden told his wife Jill, "I can picture myself sitting in the Oval Office. I can picture who I'd pick up the phone and call."

It turns out that Biden is getting calls from the president, not making them. But he's taken to the supporting role nonetheless, as he re-redefines the job of vice president after Dick Cheney's unprecedented grasp on the levers of power in the George W. Bush administration.

Biden's to-do list was defined at the outset by two central issues for President Barack Obama: keeping the U.S. on track to get out of Iraq and making sure that hundreds of billions of economic stimulus dollars are spent swiftly and smartly. And nothing illustrates how he has cemented his personal relationship with Obama better than his behind-the-scenes role as skeptic-in-chief in hour upon hour of private deliberations over what the U.S. should do next in Afghanistan.

"You can always count on him to ask probing questions, and he has," says David Axelrod, a senior adviser to Obama.

Biden is busy. Phone calls to foreign leaders alternate with mediating disputes between governors and mayors over how to spend highway money. Flights to Baghdad are interspersed with trips to Boston. His policy turf has expanded as Obama calls on him to cajole for health care votes, tend to U.S. alliances abroad, promote nuclear nonproliferation and take on more political appearances as the midterm election season approaches.

He's made eight foreign trips this year, including three to Iraq. And next week he's off to meet leaders in Poland, Romania and the Czech Republic who have a big stake in the administration's revamped plans for a European missile shield. On Capitol Hill, the vice president makes it a point to hit the StairMaster in the Senate gym at least once a week, to help stay connected to former colleagues.

Over the months, Obama and Biden gradually have gotten more comfortable with one another in their respective roles as decider and adviser_ something not initially taken for granted.

Early on, "there was a lot of uncertainty" about how Obama would use Biden, says Ron Klain, the vice president's chief of staff, adding that the chemistry between the two has worked out better than some had expected.

"Their most important interactions," says Axelrod, "are interactions that no one actually sees."

That's not to say that Biden's transition from lone ranger to a supporting role under Obama has been seamless.

At age 66, Biden ever will be Biden, and that means a shoot-from-the-lip style that feeds stereotypes of him as both a straight talker and a gaffe machine.

Over-the-top rhetoric that might have provoked a mere eye-roll when he was a senator looms larger when uttered as vice president. Critics point to any number of off-key notes: Biden angered Russia with his comments about its "withering economy;" he irked Iraq's leaders by pushing them to be more accountable; he triggered a day of backtracking after swearing off trains and planes because of swine flu worries.

And when Biden declared that no matter how hard the administration tries to do right, "there's still a 30 percent chance we're going to get it wrong," he got a public poke from Obama.

He's learning how to be effective in his job as vice president, being supportive to the president, without losing the quirks that make him Joe Biden.

Axelrod waves off the significance of such incidents.

"Everybody's strength is also their weakness," Axelrod says. "Biden is honest. He's blunt, sometimes to a fault, but the trade-off isn't even close."

Biden's vice presidency is shaping up as a mix of his two Democratic predecessors, two of the most influential vice presidents after Cheney. Walter Mondale served primarily as a troubleshooter and adviser to Jimmy Carter and avoided specific projects. Al Gore went all-out for Bill Clinton on a handful of signature issues, notably climate change and "reinventing" government, and put a premium on being part of the public tableau whenever Clinton made an appearance.

Mondale, who met with Biden three times as he prepared for the job, said it takes time for a new vice president to find his "sweet spot" after some initial shuffling around, and that Biden appears to have found his niche, mixing the private counselor's role with a full slate of responsibilities for specific programs.

Biden wound up with oversight of the government's mammoth $787 billion stimulus plan after he wrote Obama a memo about how it should be run, and he's clearly relishing his role as the program's top cop. The vice president holds weekly conference calls with mayors, governors and others to press for wise use of the money, and he calls regular Cabinet meetings to keep the Washington end of the program on track, too. He's imposed a 24-hour rule for answering local officials' questions.

Ed Deseve, the president's chief executive of the stimulus, says Biden told him early on, "I'm really going to do this hard; I'm not going to do this soft."

At a recent Cabinet meeting, Biden pressed federal officials to give him a quick heads-up when projects don't move forward on schedule, saying, "You've gotta give me more ammo so I can pick up the phone and be the sheriff."

When Sen. Pat Roberts, R-Kan., complained recently that two stimulus projects in Kansas could result in the same highway being paved twice, Biden was on the phone with transportation officials within minutes demanding they "get this damn thing fixed right now," says Deseve. And it was.

South Carolina Comptroller Richard Eckstrom, who oversees stimulus spending in his state, says Biden may be "giving it all he's got," but states haven't been given the tools they need to meet federal requirements, in particular reporting rules that arrived without money to help states meet them.

"Nebulous Washington didn't think this one through very well," Eckstrom said.

Iraq, the other big item on Biden's list, also takes a significant chunk of the vice president's time, and that's only going to increase as January's Iraqi national elections approach. He's expected to be back in Baghdad for a fourth time before year's end.

Once the those elections are passed, Biden is likely to devote more time to nuclear nonproliferation and developing a strategy for U.S. ratification of the Comprehensive Test Ban Treaty, which would outlaw all nuclear bomb tests.

Biden, best known in the Senate for his foreign policy credentials, jokingly told an audience earlier this year that "I don't do health care."

Nonetheless, he's spending increasing amounts of time pressing the president's case for overhaul legislation with former Senate colleagues. He's talked multiple times with every Democrat on the pivotal Senate Finance Committee, which approved a version of the measure on Tuesday, both in one-on-one meetings and more casual contacts at the gym or over dinner. His staff is instructed to put through senators' calls without delay.

As the midterm U.S. elections near, Biden's schedule also is getting more crowded with political appearances on behalf of Democrats around the country.

The announcement that he'll speak at Iowa's Jefferson Jackson Day dinner next month stoked talk that Biden, who's already run for president twice, might harbor thoughts of another run in 2016, when he'd be 77. Biden's made a point not to close that door, but Klain says the vice president's visit to Iowa is more about helping Democrats on the ticket in 2010 and building party strength for 2012.

Team Biden says the vice president's next goal is to avoid taking on too much.

"What is at risk of getting squeezed is his availability and his time to be briefed for and to participate in meetings with the president," says Klain. "The president seems to have his eye on the same thing."

It is telling, says Klain, that Obama's staff checked in with Biden's to make sure he'd be in town before they scheduled this month's Afghan policy review meetings.

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